http - Flutter 内置值反序列化'由于 : Tried to build class but nested builder for field threw: Tried to construct class with null field 而失败

Question

我正在为我的 PODO 类使用构建值

以下是我的代码

library mobile_login_model;

import 'package:built_value/built_value.dart';
import 'package:built_value/serializer.dart';

part 'mobile_login_model.g.dart';

abstract class MobileLoginModel implements Built<MobileLoginModel, MobileLoginModelBuilder> {
  MobileLoginModel._();

  factory MobileLoginModel([updates(MobileLoginModelBuilder b)]) = _$MobileLoginModel;

  @BuiltValueField(wireName: 'status')
  int get status;
  @BuiltValueField(wireName: 'msg')
  String get msg;
  @BuiltValueField(wireName: 'data')
  MobileLoginData get data;

  static Serializer<MobileLoginModel> get serializer => _$mobileLoginModelSerializer;
}


abstract class MobileLoginData implements Built<MobileLoginData, MobileLoginDataBuilder> {
  MobileLoginData._();

  factory MobileLoginData([updates(MobileLoginDataBuilder b)]) = _$MobileLoginData;

  @BuiltValueField(wireName: 'userid')
  String get userId;
  @BuiltValueField(wireName: 'mobile')
  String get mobile;

  static Serializer<MobileLoginData> get serializer => _$mobileLoginDataSerializer;
}

以下是我点击提交按钮时的http代码

 Future<MobileLoginModel> submitMobileNumber(String mobile) async {
    final response = await http.post(LOGIN_MOBILE_NUMBER_URL,body: {
      "mobile": mobile
    });

    MobileLoginModel mobileLoginModel = standardSerializers.deserializeWith(MobileLoginModel.serializer, json.decode(response.body));
    return mobileLoginModel;
  }

每当我输入手机号码并单击提交按钮时，http 请求就会被触发。如果我输入正确的数字那么一切正常但是假设我输入了错误的数字，我在控制台中收到以下错误

E/flutter (19934): [ERROR:flutter/shell/common/shell.cc(184)] Dart Error: Unhandled exception:
E/flutter (19934): Deserializing '[status, 0, msg, Invalid Mobile Number.]' to 'MobileLoginModel' failed due to: Tried to build class "MobileLoginModel" but nested builder for field "data" threw: Tried to construct class "MobileLoginData" with null field "userId". This is forbidden; to allow it, mark "userId" with @nullable.
E/flutter (19934): #0      BuiltJsonSerializers._deserialize (package:built_value/src/built_json_serializers.dart:154:11)
E/flutter (19934): #1      BuiltJsonSerializers.deserialize (package:built_value/src/built_json_serializers.dart:105:18)
E/flutter (19934): #2      BuiltJsonSerializers.deserializeWith (package:built_value/src/built_json_serializers.dart:35:12)
E/flutter (19934): #3      MobileLoginApiProvider.submitMobileNumber (package:dice_clutter/resources/mobile_login/mobile_login_api_provider.dart:18:61)
E/flutter (19934): <asynchronous suspension>
E/flutter (19934): #4      MobileLoginRepository.submitMobileNumber (package:dice_clutter/resources/mobile_login/mobile_login_repository.dart:16:35)
E/flutter (19934): <asynchronous suspension>
E/flutter (19934): #5      MobileLoginBloc.submitMobileNumber (package:dice_clutter/bloc/mobile_login/mobile_login_bloc.dart:22:41)
E/flutter (19934): <asynchronous suspension>
E/flutter (19934): #6      _SubmitMobileNumberState.submitMobileNumber.<anonymous closure> (package:dice_clutter/screens/mobile_login/mobile_login.dart:177:25)
E/flutter (19934): #7      _RootZone.runUnary (dart:async/zone.dart:1379:54)
E/flutter (19934): #8      _FutureListener.handleValue (dart:async/future_impl.dart:129:18)
E/flutter (19934): #9      Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:642:45)
E/flutter (19934): #10     Future._propagateToListeners (dart:async/future_impl.dart:671:32)
E/flutter (19934): #11     Future._complete (dart:async/future_impl.dart:476:7)
E/flutter (19934): #12     _SyncCompleter.complete (dart:async/future_impl.dart:51:12)
E/flutter (19934): #13     _AsyncAwaitCompleter.complete (dart:async/runtime/libasync_patch.dart:28:18)
E/flutter (19934): #14     _completeOnAsyncReturn (dart:async/runtime/libasync_patch.dart:295:13)
E/flutter (19934): #15     checkInternetConnection (package:dice_clutter/helpers/internet_connection.dart)
E/flutter (19934): <asynchronous suspension>
E/flutter (19934): #16     _SubmitMobileNumberState.submitMobileNumber (package:dice_clutter/screens/mobile_login/mobile_login.dart:174:5)
E/flutter (19934): #17     _SubmitMobileNumberState.build.<anonymous closure>.<anonymous closure> (package:dice_clutter/screens/mobile_login/mobile_login.dart:151:31)
E/flutter (19934): #18     _InkResponseState._handleTap (package:flutter/src/material/ink_well.dart:507:14)
E/flutter (19934): #19     _InkResponseState.build.<anonymous closure> (package:flutter/src/material/ink_well.dart:562:30)
E/flutter (19934): #20     GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:102:24)
E/flutter (19934): #21     TapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:242:9)
E/flutter (19934): #22     TapGestureRecognizer.handlePrimaryPointer (package:flutter/src/gestures/tap.dart:175:7)
E/flutter (19934): #23     PrimaryPointerGestureRecognizer.handleEvent (package:flutter/src/gestures/recognizer.dart:315:9)
E/flutter (19934): #24     PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:73:12)
E/flutter (19934): #25     PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:101:11)
E/flutter (19934): #26     _WidgetsFlutterBinding&BindingBase&GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:180:19)
E/flutter (19934): #27     _WidgetsFlutterBinding&BindingBase&GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:158:22)
E/flutter (19934): #28     _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerEvent (package:flutter/src/gestures/binding.dart:138:7)
E/flutter (19934): #29     _WidgetsFlutterBinding&BindingBase&GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:101:7)
E/flutter (19934): #30     _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:85:7)
E/flutter (19934): #31     _invoke1 (dart:ui/hooks.dart:168:13)
E/flutter (19934): #32     _dispatchPointerDataPacket (dart:ui/hooks.dart:122:5)  

Answer 1

因为接收到的 JSON 中缺少 data 属性 {"status": 0, "msg": "Invalid Mobile Number." 它需要为空.默认情况下，所有属性都是不可空的。

  @nullable
  @BuiltValueField(wireName: 'data')
  MobileLoginData get data;

https://pub.dartlang.org/documentation/built_value/latest/built_value/nullable-constant.html